Secondly, enable Spamassassin for your email accounts via your
control panel. SPAM can then be marked with *****SPAM***** in the header, and
you can filter this out into Trash/Spam folders by downloading email using a
mail client such as Microsoft Outlook or Mozilla Thunderbird.

Thirdly,
enable your default catch all email address to ":fail: no such user here". This
will bounce all SPAM emails being sent to random email addresses using your
domain name. If you use a real email address, then all random SPAM will end up
in your inbox for that email address.

Fourthly, avoid using an
auto-responder. This is because an auto-responder will confirm that the email
address is valid, and SPAM robots will then know to send more SPAM to such an
email.

These are some steps that can be taken to avoid SPAM, but much of
it depends on you thinking very carefully about how to make it difficult for
SPAM to get through.